Determination device for size of cutting block using connection device

ABSTRACT

Disclosed is a determination device for the size of a cutting block. The determination device includes the connection device mounted to a tibia to be placed at a top surface thereof along an upper line of a predetermined flexion gap; a body including a slide groove on a central portion of a front surface thereof, a bent part on an upper portion thereof to be placed at a precut anterior cortex of a femur, and a plurality of graduations provided on the body to determine the size of the cutting block; a slider to be slidably engaged with the slide groove of the body and including an indicating line on an upper portion thereof, and a guide to be assembled with the slider and come into surface contact with the top surface of the connection device at a lower portion thereof. The conventional devices are problematic in terms of being incapable of determining a cutting block suitable for the damaged state of a knee joint of a patient because the size of the cutting block is determined by measuring only the height of the femur with no consideration of a flexion gap. The problem encountered in the prior art can be overcome by using the determination device for the size of the cutting block according to the present invention.

TECHNICAL FIELD

The present invention relates, in general, to a determination device forthe size of a cutting block using a connection device. Moreparticularly, the present invention relates to a determination devicefor the size of a cutting block used to determine the size of a cuttingblock which determines the standard size of an artificial joint toreplace a worn, damaged or diseased knee joint upon knee arthroplasty,using a connection device as described in Korean Pat No. 10-399489 or anequivalent thereof.

BACKGROUND ART

Knee arthroplasty has become one of the most commonly performedsurgeries, with which a damaged or deformed knee joint due to congenitaldeformation, traumatic injuries, diseases, degenerative arthritis, etc.is removed and replaced with an artificial joint. In brief, referring toFIG. 1, the anterior cortex 15 is first cut according to the damaged ordeformed state of a knee joint of a patient. And, an extension gap isdetermined to allow for bone cutting matching with the size of anartificial joint (prosthesis). The femur 10 is undercut according to theextension gap. In addition, according to the determined extension gap,referring to FIG. 2, a flexion gap is determined based on an upper endof the tibia 20. Then, referring to FIG. 3, the posterior condyles 11,the posterior chamfer 12, the anterior cortex 13 and the anteriorchamfer 14 of the femur 10 are cut using an appropriate femoral cuttingblock 30. An artificial joint is then implanted to replace the cut kneejoint.

The flexion gap, which is required for the knee to be flexed from anextended (straight) position, indicates the gap between the cut surfaceof the upper end of the tibia 20 and the cut surface of the posteriorfemoral condyles 11. Since the femur and the tibia rotate at a state ofbeing in close contact with each other, the flexion gap is typicallydetermined to be identical to the extension gap. However, the flexiongap may be determined according to 3-D shape of the damaged knee jointof a patient.

On the other hand, the femoral cutting block 30, used upon the posteriorand anterior cuts at the posterior condyles 11, the posterior chamfer12, the anterior cortex 13 and the anterior chamfer 14 of the femur 10,is commercially available in a standardized size corresponding to thesize of the flexion gap. Therefore, the femoral cutting block 30 isdetermined to have a size corresponding to that of the determinedflexion gap, while the size of the artificial joint is determinedaccording to the size of the femoral cutting block.

However, conventional devices for determining the size of a cuttingblock are problematic in terms of being incapable of determining acutting block with a proper size because the size of the cutting blockis determined by measuring only the height of the femur without anyconsideration for the size of a flexion gap that varies depending on thesize of the cutting block.

Referring to FIG. 4, the problem of the conventional devices fordetermining the size of the cutting block will be described in detail,as follows. A conventional device 40 for determining the size of thecutting block includes a support 41 to be placed at the posteriorfemoral condyles 11 and a bar 42 to be placed at the anterior femoralcortex 15. The bar 42 is slidably connected with the support 41 and hasa predetermined number of graduations. The support 41 includes anindicating line. A graduation of the bar is determined, which is alignedwith the indicating line of the support 42, by closely contacting thesupport 41 and the bar 42 with the position femoral condyles 11 and theanterior femoral cortex 15, respectively. The measured graduationbecomes to the size of a cutting block 30, and thereby the size of anartificial joint is determined.

However, there is a significant problem experienced in this conventionaldevice 40 for determining the size of the cutting block. That is, thegraduation of the bar indicated by the indicating line is changed by thedamaged or deformed state of the posterior femoral condyles, by the cutdegree of the anterior femoral cortex or by the total height of thefemur, thereby the size of the cutting block is varied.

As described above, the flexion gap is the gap between the cut surfaceof the upper end of the tibia 20 and the cut surface of the posteriorfemoral condyles 11, and the size of the cutting block should bedetermined by the flexion gap. However, since the conventional devicesdetermine the size of the cutting block by only the height of the femurwithout any consideration of the flexion gap, the devices have theproblem of being incapable of determining the cutting block with aproper size to allow a surgeon to perform a bone cutting operation todefine a desired flexion gap.

If a cutting block with an unsuitable size is determined, a determinedartificial joint has also an unsuitable size. This unsuitable prosthesisresults in a limitation in normal physical behavior. Consequentially,extension and flexion exercises of the knee are not normal, and animbalance occurs between the muscle and the ligament that constitute theknee joint.

DISCLOSURE OF THE INVENTION

The present invention has been made keeping in mind the above problemsoccurring in the prior art, and an object of the present invention is toprovide a determination device for the size of a cutting block using aconnection device as described in Korean Pat. No. 10-399489 or anequivalent thereof.

In order to accomplish the above object, the present invention providesa determination device for the size of a cutting block using aconnection device, including the connection device mounted to a tibia tobe placed at a top surface thereof along an upper line of apredetermined flexion gap; a body including a slide groove on a centralportion of a front surface thereof, a bent part on an upper portionthereof to be placed at a precut anterior cortex of a femur, and aplurality of graduations provided on the body to determine the size ofthe cutting block; a slider to be slidably engaged with the slide grooveof the body and including an indicating line on an upper portionthereof; and a guide to be connected with the slider and come intosurface contact with the top surface of the connection device at a lowerportion thereof.

The aforementioned object of the present invention will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a view showing an extension gap;

FIG. 2 is a view showing a flexion gap;

FIG. 3 is a view showing a cutting block;

FIG. 4 is a perspective view of a conventional device for determiningthe size of a cutting block;

FIG. 5 is a perspective view of a determination device for the size of acutting block according to the present invention;

FIG. 6 is a sectional view taken along the line A-A′ of FIG. 5; and

FIG. 7 is a view showing application of the determination device of thepresent invention to a flexed knee joint so as to determine the size ofa cutting block.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to the accompanying drawings, an embodiment of thepresent invention will be described in detail. Referring to FIG. 5, adetermination device 100 for the size of a cutting block includes aconnection device 110, a body 120, a slider 130 and a guide 140.

The connection device 110 may be a connection device as described inKorean Pat. No. 10-399489 or an equivalent thereof. The connectiondevice 110 includes a supporting part 111 on an upper portion thereof, afixation part 112 on a lower portion thereof and a side plate 113. Inthe connection device 110, the support part 111 is integrated with thefixation part 112 into a single body by the side plate 113. A pluralityof pin holes 114 are provided on the fixation part 112 at regularintervals.

The body 120 has a quadrilateral shape, and is formed with a slidegroove 121 on a central portion of a front surface thereof, and with abent part 122 on an upper portion thereof. A slider 130, which will bedescribed in detail below, is slidably engaged with the slide groove121. The bent part 122 is safely placed at the precut posterior cortex15 of the femur. In addition, preferably, a plurality of inclined pinholes 123 are formed on a side surface of the body 120. The body 120 maybe fixed to the femur by a Pin P passing through each of the pin holes123 and by being inserted into the femur. Since the body may be fixed tothe femur, it is possible to correctly measure the size of the femur.Further, a plurality of graduations 125 are provided on a front surfaceof the body 120, which correspond to the sizes of commercially availablecutting blocks. Preferably, an additional bone cutting crevice 124 isprovided on the upper portion of the body 120 to execute an additionalcutting of the anterior femoral cortex. If necessary, the anteriorfemoral cortex 15 may be further cut by inserting a vibratory saw intothe cutting crevice 124.

The slider 130 is slidably engaged with the slide groove 121 of the body120, and includes an indicating line 131 on an upper portion thereof tomeasure a graduation of the body 120. Preferably, as shown in FIG. 6, aguide groove 132 is provided in a vertical direction on a rear surfaceof the slider 130. A protruding pin 127 is forcibly inserted into thebody 120 from the rear surface of the body 120 to be guided along theguide groove 132. By this protruding pin 127, the body 120 and theslider 130 are not separated from each other. In addition, a lockingbolt 126 is preferably provided on a front surface of the slider 130 tofix the slider 130 to a predetermined position of the body 120.

The guide 140 is connected with the slider 130 and comes into surfacecontact with the top surface of the connection device 110 at a lowerportion thereof. Also, the guide 140 is marked with a sign (141), whichincludes an L (Left) or R (Right) sign, to be applicable to both rightand left knee arthroplasties by being reversibly inserted into theslider 130. Preferably, the guide and the slide are interconnected by acheck ball (not shown).

Referring to FIG. 7, the practical application of the determinationdevice for the size of the cutting block according to the presentinvention will be described below.

First, an extension gap as shown in FIG. 1 is measured according to thedamaged or deformed state of a knee joint of a patient, and a flexiongap is determined depending on the measured extension gap. The flexiongap is typically determined to be identical to the extension gap, but isoften determined just by experience of a surgeon based on a differencein 3-D shape of the knee joint between a healthy person and the patient.

Two pins (P′) are respectively inserted through two he pin holes 114each provided at each of the right and left locations of the connectiondevice 110 matching to the measured extension gap, thus being driveninto a tibia 20. The connection device 110 is then removed from the kneejoint. Thereafter, a bone cutter 150 for the top-cutting of the tibia 20is inserted into the two pins (P′) driven in the tibia 20. Thereafter,the connection device 110 is again inserted into the two pins (P′) toposition the bottom surface of the flexion gap on the same line as thebone cutting crevice 142 of the bone cutter 150 and to position the topsurface of the flexion gap on the top surface of the support part 111 ofthe connection device 110.

Subsequently, the determination device for the size of the cutting blockaccording to the present invention is placed on the femur 10 of the kneeat a flexion position. As a result, the bent part 122 of the body 120 isplaced at a precut anterior cortex 50 of the femur 10, while the guide140, on a lower surface thereof, comes into surface contact with the topsurface of the connection device 110. Then, the slider 130 connectedwith the guide 140 slides along the slide groove 121 of the body 120.

When the slider 130 is stopped, one graduation of the body 120 indicatedby the indicating line 131 of the slider 130 is checked among theplurality of graduations 125 of the body 120. The measured graduationdesignates the size of a cutting block for cuts at the posteriorcondyles 11, the posterior chamfer 12, the anterior cortex 13 and theanterior chamfer 14 of the femur 10, which are shown in FIG. 3, anddesignates the size of an artificial joint as a replacement for thedamaged knee joint.

If necessary, the body 120 may be fixed to the femur 10 via the pin (P).Furthermore, the anterior cortex 15 of the femur 10, which is shown inFIG. 4, may be additionally cut via the additional bone cutting crevice124. Also, the slider 130 may be fixed to the body 120 by the lockingbolt 126. The guide 140 may be applicable to both right and left kneearthroplasties by being reversibly inserted into the slider 130.Furthermore, the slider 130 and the guide 140 may be integrated into asingle body.

INDUSTRIAL APPLICABILITY

As described hereinbefore, the determination device for the size of acutting block according to the present invention allows for thedetermination of a cutting block with a size matching to a determinedflexion gap. Therefore, the present determination device is advantageousin terms of facilitating the selection of an artificial joint securing anormal physical behavior of a patient and thus allowing the patient toperform active extension and flexion exercises of the knee after kneejoint replacement.

1. A determination device for a size of a cutting block, comprising: aconnection device, comprising a supporting part having a flat topsurface on an upper portion thereof, a fixation part on a lower portionthereof, a side plate, a plurality of holes formed on the fixation part,and a plurality of pins to be inserted through the holes for placing theflat top surface of the supporting part on an upper line of apredetermined flexion gap, the connection device is adapted to be fixedto a tibia by driving at least two of the plurality of pins throughcorresponding holes into the tibia; a body including a slide grooveformed on a central portion of a front surface thereof, a bent partformed on an upper portion for safely mounting a precut anterior cortexof a femur on the bent part, and a plurality of graduations provided onthe body to determine the size of the cutting block; a slider slidablyconnected with the slide groove of the body and including an indicatingline on an upper portion thereof; and a guide, adapted to be placed on afemur, including an end fixed to the slider and a flat bottom surface ofthe guide coming into surface contact with the flat top surface of thesupporting part of the connection device so as to stop a slidingmovement of the slider and to place the flat bottom surface of the guideon the upper line of the predetermined flexion gap wherein the slider isplaced so that length directions of the slider and the femur areperpendicular or substantially perpendicular, wherein the guide ismarked with right and left directions to be applicable to both right andleft knee arthroplasties by being reversibly inserted to the slider. 2.The determination device of claim 1, wherein the body, on a side surfacethereof, has a plurality of pin holes through each of which a pinpasses.
 3. The determination device of claim 1, further comprising alocking bolt to fix the slider to the body.
 4. The determination deviceof claim 1, wherein the slider comprises a guide groove formed in avertical direction on a rear surface of the slider, and the bodycomprises a protruding pin forcibly inserted into the body from a rearsurface of the body to be guided along the guide groove.
 5. Thedetermination device of claim 1, wherein the body comprises anadditional bone cutting crevice formed on an upper portion thereof toexecute an additional cutting of the anterior femoral cortex.
 6. Thedetermination device of claim 1, wherein the slider and the guide areintegrated into a single body.